The present invention relates to durable and flexible coverings for chemical and biological protection. More specifically, the invention relates to materials and articles that can be used to afford good protection of persons or contents from exposure to hazardous or noxious agents in the form of liquids, aerosols, vapors, or particulates. Furthermore, the present invention relates to coverings that provide protection for an adequate period of use and for conditions of use intended for protective materials. The durable and flexible coverings for chemical protection provided in accordance with this invention are particularly suited for applications such as articles of clothing, tents, sleeping bags, and the like.
The coverings, as described herein, are used to prevent the transmission of hazardous or noxious chemical and biological agents through their thickness by repelling and adsorbing, absorbing, reacting or otherwise binding, degrading, or destroying such agents. These coverings may be utilized to protect a wearer, user, or contents contained within such coverings from exposure to these hazardous or noxious chemical and biological agents. These agents are often presented in an external environment, outside of the covering, and it is desired to protect the environment contained inside the covering from substantial exposure to such agents. In other instances, as will be described, it may be desired to retain, destroy, or otherwise degrade chemicals in the area internal to the covering. Most significantly it is the aim of this invention to provide this performance for the intended period of use and through the rigors of use.
A number of different means have been described or attempted to provide adequate protection from chemical and biological agents. Well known in the art is the general approach of incorporating materials that are capable of adsorbing the hazardous chemicals. Adsorptive chemical protective systems work by adsorbing the hazardous chemicals into sorbants. Other approaches incorporate chemicals or other components that will react and bind or degrade the hazardous agents, including the catalytic breakdown of such agents. All of these approaches attempt to provide sufficient quantities of adsorptive or catalytic materials to effectively address the necessary level of protection from harmful agents. However, unable to withstand the rigors of use, they fail to provide protection over the intended life and for the intended application of the protective systems. Thus while some address aspects of initial performance, satisfactory performance over the course of use is not achieved. Examples of such approaches are well known, and can be found in a number of patents, such as U.S. Pat. No. 4,510,193 to Blucher et al.
During use protective coverings are exposed to various environments and conditions that lead to performance degradation. Particularly severe are conditions associated with protective coverings employed as protective clothing. Protective clothing is often used when handling dangerous or hazardous materials, for example, in what is commonly referred to as Hazmat applications. Also, protective clothing has been utilized in the protection of civilian and military personnel during the threat of exposure to chemical warfare agents, dangerous biological agents, or otherwise hazardous materials.
If the protective performance of such clothing degrades significantly, a dangerous or even life-threatening situation for the wearer develops with continued use of the system. It is critical to design materials capable of performing well initially, and that are capable of maintaining high performance levels over time and through the rigors of use. Attempts to provide high level long-term performance have resulted in a compromise of design considerations yielding undesirable properties. For example, where monolithic layers are used in protective clothing to provide long-term protection, undesirable conditions may result in physiological stresses being imposed on a wearer. Moreover, by the nature of its use, protective clothing should be flexible, however, flexing can cause the protective components to become dislodged or damaged. Protective clothing can also be subject to a significant amount of abrasion and impact, for example on the knees of trousers. These physical stresses can cause a loss of carbon particulates or beads from the structure reducing protection levels. Additionally, activated carbon fabrics, including carbonized and activated polyacrylonitrile textiles, may become broken and their structures disrupted, potentially leaving localized areas with less than desired levels of adsorptive materials. Physical damage resulting in loss of adsorbent or other protective materials can result in protection levels that are undesired, and even unsafe.
Performance degradation of protective materials also results from exposure to contaminants. For example, when brought into contact with adsorbent materials, various liquid contaminants may be adsorbed or can coat the adsorbents such that their protective performance is severely compromised. Liquid contaminants may include petroleum-based contaminants including diesel fuel and various lubricants or, for example in the case of fire-fighting or rescue uses, materials such as fire-fighting foams or even human blood. Additionally, hazardous chemical agents that present a liquid challenge, for example in the form of liquid drops, can wet into a protective material and directly contact the adsorbents. This will create an extremely high concentration challenge, often overwhelming the adsorption rate and capacity of adsorbents or other functional materials, and resulting in undesired permeation levels of the chemical through the protective covering.
Further, many applications may require that the protective covering undergo repeated cycles of washing and drying. Cycles of washing and drying, particularly with the addition of detergents that can be adsorbed into materials such as activated carbon, present both physical damage and a chemical contamination challenge to the protective materials. Significant degradation of protective performance can often result.
Protective clothing in particular is also subject to contamination from the environment internal to the protective covering such as the environment created by the wearer or user. The wearer can produce significant quantities of sweat, sebum, and other body oils. These materials are capable of contaminating the adsorbents or other functional materials contained in the clothing and can degrade their effectiveness, reducing the protection offered. There also are instances where it may be desired that the protective coverings restrict transmission of agents from the interior area of the covering to the external area. For example, in some applications such as hunting, it may be desired to prevent odiferous vapors or particles from moving through the protective covering to the outside environment, where they might be detected. It is also possible during the course of use that chemical agent vapors may enter the interior area of the protective covering. In the case of protective clothing, agent access may be through cuffs or zippers, or other closures. Where there is leakage into the interior area of the protective covering, such vapors can be absorbed by the skin of the person within the clothing. Current protective constructions using continuous layers of adhesives or films positioned between the wearer and the adsorptive materials in the protective clothing can restrict the passage of agents away from a wearer increasing exposure.
Prior efforts, such as described in U.S. Pat. No. 5,190,806 by Nomi teach the addition of an air impermeable continuous adhesive layer to prevent the passage of liquid contaminants through an outer layer to the inner adsorptive layer. However, constructions incorporating monolithic continuous layers of polymeric films or adhesives will significantly reduce the transmission rate of moisture vapor, or what is commonly also known as “breathability”. In the case of protective clothing, this reduction in transmission of moisture vapor will result in significantly increased physiological stresses. The incorporation of air impermeable continuous materials into the construction, may remain “breathable”, but require that moisture vapor first absorb into the continuous layers, diffuse through these physical materials, and subsequently evolve from the layers through a solution-diffusion mechanism. Constructions which result in the solution-diffusion process for moisture vapor transport generally result in lower rates of the transport of moisture vapor.
In order to minimize the physiological stresses imposed by the protective covering, it would be desirable to maintain physical passages throughout the protective structure which allow for diffusive transport of moisture vapor. Contiguous air pathways from the internal to the external environments will allow moisture vapor to move through these pathways via a diffusive mode through air. Air permeable constructions in which moisture vapor transport may occur through diffusive transport through air have a higher moisture vapor transport rate (MVTR) than constructions wherein moisture vapor transport is through solution-diffusion. It would be desirable to have a protective construction that maximizes the moisture vapor transport rate in order to minimize the physiological stress, and thus it is desired to maintain contiguous air passages through the protective covering structure.
However, it is also well known that hazardous agents may present themselves in the form of aerosols or particulates. Thus, contiguous air passages through the protective covering structure, if too large in diameter, can allow the direct passage of such agents from the external to the internal environment within the covering. Particularly where agents are carried by wind or other forced flow, protective coverings with large air passages can allow significant transmission of those agents. Previous efforts, such as in WO 83/02066 to Nilsen, have incorporated microporous films to overcome this issue. However, the passage of contaminants and some chemical agents was not prevented where some materials were capable of wetting into and through the described films.
Another way in which coverings for protection against hazardous or noxious chemicals have been previously designed to address physical and contaminant degradation of performance is to incorporate levels of protective materials far beyond what would be necessary without occurrences of degradation. Adding substantially greater quantities of adsorptive materials to the protective coverings, such as activated carbon, can potentially offset the levels of performance degradation. However, in addition to added cost the result is much heavier and bulkier systems than desired.
Applications of protective clothing are particularly sensitive to additional bulk and weight. Added weight presents a greater physical burden to the wearer. It is well known that added thickness and bulk of the protective clothing can substantially reduce the moisture transport from the wearer to the outside environment, as well as create a greater resistance to heat transport, resulting in significantly greater physiological stresses. Furthermore, increased bulk and weight are also undesired characteristics for the packaging, storage, handling, and transportation of these materials. Thus, current solutions have often balanced the need to maintain the performance of protective coverings over the course of their use, despite physical and contamination challenges, and the need to maintain conditions adequate for physiological comfort and safety.
What is greatly desired, and heretofore undisclosed in the art, is a durable protective covering that is not subject to performance degradation. That is, it is desired for the properties of the protective covering to be largely unaffected by physical use, by external contaminants, or by internal contaminants. It is further desired that this protective covering is comfortable and flexible, and minimizes the physiological burden on the user. And it is further desired that this protective covering be capable of preventing the passage of agents in the various forms of liquids, vapors, aerosols, and particulates. Accordingly, a primary purpose of the present invention is to provide a durable covering for protection against hazardous, noxious, or otherwise harmful chemical and biological agents which simultaneously achieves the above objectives.
These and other purposes of the present invention will become evident from review of the following specification.